Centrifugal pumps having axially split, also known as horizontally split, casings are well known in the industry. In fact, such pumps have been manufactured for at least 100 years.
Axially split pumps may have single or double volute casings. FIG. 1 depicts a conventional double volute centrifugal pump 10 having an axially split casing 12. The axial split in casing 12 permits easy separation and service of the internal components. Thus, the pump casing 12 has a lower half 12a and an upper half 12b. Standard components of centrifugal pump 10 include a shaft 14, bearing housing 16, bearing 16a and an impeller 17. Shaft 14 is driven by a prime mover (not shown). Bearings 16a rest in conventional bearing seats, not shown. Impeller 17 also has impeller wear surfaces 17a which rest in impeller seats, not shown. The other conventional components, such as suction and discharge nozzles, identified as 13 and 15 respectively, and other characteristics of centrifugal pump 10 are well known to those skilled in the art and will not be further discussed.
Design changes have been rare in the field of centrifugal pumps having axially split casings. Currently available pumps have relatively long life spans when serviced regularly. However, improvements which reduce the cost of manufacturing and improve serviceability of the conventional pump remain desirable. Conventional pump design utilizes gasket material 19 between the flanges 18a and 18b of the lower and upper casing halves 12a and 12b. As known to those skilled in the art, gasket material 19 is cut to match the machined surfaces of flanges 18a, 18b. When clamped between flanges 18a, 18b, gasket material 19 provides sealing capabilities to compensate for variations in the machined surface of the joined components. To provide the necessary seal at the desired operational pressures, conventional pumps 10 utilize flanges having thicknesses of about 2 inches to about 6 inches. However, even with the robust flange thickness, the bolted joint permits pump operational pressures of only about 150 psi to about 300 psi.
The manufacturing process of currently available centrifugal pumps is constrained by the requirement to use a gasket to effect a seal between lower and upper casing halves 12a, 12b. Current manufacturing processes must consider the thickness of gasket material 19 with regard to machining of lower and upper casing halves 12a, 12b. As a result, gasket material 19 becomes part of the assembly tolerances between casing halves 12a, 12b. Thus, the inter-relationship of gasket material 19, and casing halves 12a, 12b precludes subsequent substitution of casing halves. As a result, casing halves 12a, 12b for each pump are mated for life, i.e. one cannot use a substitute casing half to repair the pump without re-machining of each casing half.
Use of gasket material 19 also complicates subsequent service of centrifugal pump 10. Gasket material 19 must be replaced each time upper casing half 12b is removed from pump 10. Prior to reassembly, mating surfaces must be cleaned of all old gasket material and a replacement gasket installed. Thus, prior to servicing pump 10, the operator must have gasket material available for reassembly.
The present invention provides an improved seal system between flanges 118a and 118b. The improved seal system eliminates the need for a gasket positioned between the flanges and permits reduction in flange thickness. Further, the present invention permits interchangeability of casing halves. As a result, the improved seal system reduces manufacturing costs and enhances serviceability of the centrifugal pump.